The present invention relates to novel light duty liquid detergent compositions with superior grease removal and high resistance to foam collapse properties, particularly against nonemulsifier-containing food greases, containing a mixture of higher alkyl glyceryl and polyglyceryl ether nonionic surfactants, the n-glycidol distribution containing a maximum of 49% of n=1 with increasing amounts of n=2 and 3. Compositions with low amounts of n=1 and high amounts of n=2 and n=3 glycidol ethers are preferred, i.e., minimize the monoglycidol ether component and maximize the di- and tri-glycidol ether components.
The prior art discloses the use of nonionic surfactants such as ethoxylated alcohols, in detergent compositions, in order to improve removal of oily stains from fabrics, dishes and similar substrates. However, said alcohol ethoxylates have limited utility in light duty liquid detergents due to their low resistance to foam collapse and low removal capability for nonemulsifier-containing greases or oils, such as motor oils and greases, hydrocarbon oils and grease stains and the like.
U.S. Pat. No. 4,098,713 has attempted to solve this problem by using, as the surfactant, a monoglyceryl ether of an ethoxylated (containing 1-6 ethoxy groups) hydroxy-compound, the relative degrees of hydrophobic and hydrophilic characters in the compounds being regulated in order to provide adequate solubility. U.S. Pat. No. 4,206,070 and its British patent counterpart No. 1,560,083 disclose a binary surfactant system of monoglyceryl ether and an ethoxylated alcohol, said alcohol serving to solubilize the monoglyceryl ether which has insufficient water solubility to act as useful surfactants in aqueous solutions.
The monoglyceryl ethers of higher alkyl alcohols are known materials as disclosed in U.S. Pat. No. 2,028,654. The polyglyceryl ethers of aliphatic alcohols having the structural formula ##STR2## where R is a linear aliphatic hydrocarbon of 6-24 carbons and x is 4-14, useful as biodegradable wetting agents, dispersing agents and foaming agents, are disclosed in U.S. Pat. No. 3,879,475. The problem of providing sufficient water solubility to the polyglyceryl ethers defined in the aforesaid patent in order to enable them to function as useful surfactants, is overcome by the use of at least a 4/1 and preferably a 6/1 mole ratio of the reactants glycidol/alcohol.
U.S. Pat. No. 3,578,719 and No. 3,666,671 disclose nonionic surfactants having the formula ##STR3## where R may be an alkyl group of 8-20 carbons and n equals 2-10; and when n is at least equal to 1/3 of the number of carbon atoms in the lipophile chain (R), the products are detergents which are soluble in water.
U.S. Pat. No. 4,086,279 discloses nonionic surfactant compositions having solubility and stability in ionic solutions, especially in basic media, prepared by reacting a 3-30 unit polyglycerol as hydrophile with a hydrophobic glycidyl ether in sufficient quantity to substitute 4-25% of the hydroxy groups of the polyglycerol.
None of the above-mentioned patents disclose a light duty liquid detergent composition containing a mixture of higher alkyl monoglyceryl and polyglyceryl ethers, as nonionic surfactants having unexpectedly superior properties of grease removal and washing performance, especially with reference to nonemulsifier-containing food greases.
U.S. Pat. No. 3,024,273 discloses anionic detergent compositions consisting essentially of a mixture of sulfonated aliphatic mono- and poly-glyceryl ether compounds containing at least 10% of the sulfonated diglyceryl ether and the balance being a mixture of the sulfonated monoglyceryl and triglyceryl ethers. This anionic sulfonate mixture of glyceryl ether has a solubility limit of about 1% neat which is too low to be of any practical use for anything but a minor ingredient. In the two step process of preparing this sulfonated mixture, a mixture of chloroglyceryl ethers is formed. However, there is no disclosure of a mixture of the nonionic alkyl glyceryl ethers of present invention.